Speciation and Evolution

Variation

Difference in species population that creates a survival advantage

Adaptation

Structure, behaviour or process that helps an organism reproduce and survive in an environment.

Inherited over many generations in an environment.

Mutagens

Agents that cause DNA mutation

Mutation

Mistakes in DNA transcription as it’s copy from one cell to another.

Cause no effect on cells due to “non-coding DNA”

If passed through many generations, it can cause variation within species and a possible survival advantage.

Selective advantage

Mutation that provides a survival advantage

Selective Pressure

Environmental limiting factor that changes a population.

Process of change in adaptations within a population as result of selective pressure.

Jean-Baptiste Lamarck

Naturalist

Believed that species changed over time to achieve level of “Freedom”

Suggested of inheritance of acquired characteristics.

Charles Darwin

Born in England 1809

Observed that similar environments around the world contains different organisms

1859- Published On The Origin Of The Species By Means Of Natural Selection which talked about his discoveries and evidence.

Theory of Natural Selection

Stating that there’s a “struggle for existence”

Those in a species who’re better adapted will survive to reproduce.

Darwinian Fitness

Reproductive success of an organism

Theory Of Evolution

A species gradually changes over time.

5 Requirements For Theory of Natural Selection

Overproduction

Competition

Variation

Survival Of The Fittest

Speciation

Overproduction

Number of offspring produced is greater than number that survive

Competition

Organisms compete for limited resources because of overproduction

Variation

There’s variation among individuals in a population and it’ll passed onto offspring

Survival Of The Fittest

Individuals with traits that let them survive and reproduce have advantage.

Speciation

New Species arise because of accumulation of inherited variations.

Formation of a new species

Direct Evidence For Natural Selection

Fossil Record

Geology

Fossil Record

Shows changes in organisms over time.

Geology

Changes in Earth’s history can be organized into layers.

Indirect Evidence For Natural Selection

Embryology

Homology (Homologous Structures)

Analogy (Analagous Structures)

Physiological

Biochemical

Vestigal Structures

Biogeography

Embryology

similarities during organism development

Homology (Homologous Structures)

similar structures for different uses.

Analogy (Analagous Structures)

Similar structures of obvious different origin that’s adapted to similar environments at different times.

Physiological

Structure similarities between species

Ex. Many animals have hearts and brains

Biochemical

All living organisms have DNA and go similar processes

Vestigal Structures

Structures found within a species with no function

Biogeography

Existence of similar organisms that once live in similar areas due to Earth’s geography don’t live anymore today.

This explains changes in Darwins finches.

Speciation can occur in

Geographical Barriers (Allopatric Speciation)

Biological Barriers (Sympatric Speciation)

Combination of both leads to adaptive radiation

Diversification of common ancestor to variety of species with different adaptations

Geographical Isolation Can Lead To New Species Development

Barrier Splits Population and prevents interbreeding
Over time, genetic composition of each population changes independently
After many generations, populations become so different that even when barrier is removed, they can’t interbreed anymore to produce offspring.

Biological Barriers/Isolation

Physiological or behavioural change in population that causes reproductive isolation even in the same region that leads to speciation over many generations.

Gradulalism

Changes occur slowly & steadily in a linear fashion.

Large changes can occur slow and steady changes.

Punctuated Equilibrium

Long periods of stability caused unchanged populations.

Large-scale events cause changes in species.

Rapid Diversification

Divergent evolution that cause large number increase in species.

Mass extinctions

Loss of Majority of species